> The fourth edition of the World Ocean Review (WOR) focuses on sustainability and explores how that concept can guide the management of our marine environment. WOR 4 explains the key ecosystem services supplied by our seas and identifies the main threats to them. It offers an overview of current marine policy at regional and transnational level and shows how conservation and sustainable use of our oceans can be reconciled in future.

Concepts for a better world

> Prudent and sustainable use of nature’s resources has yet to become a reality. Past approaches have failed because the concept of “sustainability” is so ill-defined. Moreover, sustainability can only be accomplished if the complex linkages within the natural world are valued more accurately. For the future it is therefore vital to improve our understanding of the diverse services of ecosystems and to put a comprehensive conception of sustainability into practice.

How the sea serves us

> Many of the ecosystem services provided by the sea are threatened today by overexploitation, environmental pollution and greenhouse gases. Yet in many cases, how severely individual habitats are degraded and ecosystem services are impaired is just not known. Researchers are therefore attempting to assess the exact condition of marine ecosystems. Such analysis is important in order to plan concrete protection measures and to define critical limits and target values.

Politics and the oceans

> The oceans can only be protected if all stakeholder groups pull together. Good governance of the oceans therefore calls for participation from the local people directly affected and from the economic and policy spheres. National and international agreements are in place, enshrining comprehensive marine protection in law. However, the rules laid down need to be respected in practice.

Hope for the oceans

> The extent of the pollution and destruction of marine habitats is daunting. However, there are already numerous examples showing how marine conservation and the sustainable use of ma-rine resources can be achieved – not only through international agreements but also through measures adopted at the local level. It is also encouraging that the United Nations has declared marine conservation to be one of the major development goals for the future.